import React from 'react';
import ReactDOM from 'react-dom';

class App extends React.Component {
  add = () => {
    console.log(10);
  };
  render() {
    return (
      <div>
        hello App
        <button onClick={this.add}>+</button>
      </div>
    );
  }
}
ReactDOM.render(<App />, document.getElementById('root'));
